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POSTER PRESENTATIONS
Thursday, October 27th
Thalamic GABA in human epilepsy
Presenting author: Jullie Pan
Collaborating authors: N Avdievich, HP Hetherington. Departments of Neurosurgery, Neurology, and
Radiology, Yale University School of Medicine
Introduction: The thalamus is well known as a key relay, integration and broadcast point for all cerebral
processing. In particular, thalamic GABA-ergic interneurons believed to be critical for (linear) gain control in
such cerebral sensory and associative processing. It is therefore not surprising that many studies from both
human and animal perspectives have identified the thalamus and particularly thalamic GABA as a key issue of
interest. The SANTE trial is predicated on the thalamus serving as a key point for seizure control.
However, the in vivo detection of GABA is challenging for several reasons. Given its low concentration
(~1mM) and high degree of spectral overlap with amino acids and other brain metabolites, some form of
spectral editing is needed for unambiguous detection. Furthermore, because of known tissue (white, gray
matter) variation of GABA and its possible regional variation between the thalamus and cortical gray matter, its
measurement is preferably performed as a spectroscopic image to enable more accuracy. Thus far, the majority
of in vivo GABA measurements by MR spectroscopy have been reported in the occipital lobe, this region being
studied primarily because of limitations in measurement sensitivity. With the 7T advantage for SNR,
measurements of GABA in deeper regions have been a major target for our group. In this report we describe a
coherence transfer approach (selective homonuclear polarization transfer) to detect GABA. This method takes
advantage of the molecular structure of GABA to selectively detect the C4 protons of GABA (─OOC1-C2H2C3H2-C4H2-NH4+). We apply this approach to evaluate thalamic GABA in n=8 controls and in n=4 epilepsy
patients. All of the epilepsy patients were well controlled at the time of study (seizure free > 6months). Two of
the patients had localization related epilepsy (LRE), two with primary generalized epilepsy (defined from
clinical semiology and EEG data).
Methods: All studies are performed on an Agilent (Varian) 7T DirectDrive head only MR system using an 8x1
transceiver array. The transceiver array was used with RF shimming to optimize multiple RF distributions to
achieve 1kHz B1 transmission over large volumes sufficient for planar spectroscopic spin echo imaging with
outer volume suppression. In this study a 4th order shim insert (Resonance Research Inc.) is used with noniterative Bo shimming. A 1cm thick AC-PC angulated slice was studied taken through the mid-thalamus. In the
thalamic study, the ROI used for B0 shimming included the large majority of the entire slice with the exclusion
of a small ovoid over the frontal anterior ventricle. All studies were acquired as 16x16 spectroscopic images.
The duration of the entire study was ~80min.
Results: Thalamic GABA/NAA was 0.051±0.013 in controls while it was 0.090±0.012 in two patients with
LRE, 0.053±0.011 in two patients with PGE. As the detection of GABA includes a similarly coupled
macromolecule resonance, we also evaluated the ratio of GABA/(GABA + macromolecule, or GABA/tGABA.
In controls, this was 0.43±0.09; in the LRE patients this was 0.80±0.08, in the PGE patients 0.55±0.04. In
controls, thalamic NAA/Cr was 1.38±0.22; LRE 1.34±0.05; PGE 1.59±0.06. In the putamen, GABA/NAA was
0.053±0.007 in controls, 0.063±0.002 in LRE.
Conclusion: Preliminary data suggest that GABA measurements in the thalamus may be different between
localization related epilepsy in comparison to primary generalized epilepsy. While these four patients are
presently seizure free, it will be of interest to determine thalamic GABA in patients who continue to have
seizures.
PET imaging of microglial activation and glutamate receptor density in medically
refractory epilepsy patients and healthy controls
Presenting author: Hal Blumenfeld
Collaborating authors: Mehdi Djekidel Richard Carson, Dennis Spencer, Richard Bronen, Jullie Pan, Larry
Hirsch, Ken Vives, Colleen Malone. Aknowledgements: Amy Turner, Jamie Cyr, Corsi Maria, Shannan Henry,
Jonas Hannestad, Beate Planeta-Wilson
The CDC estimates that about 2.0 million people in the United States have epilepsy and nearly 140,000
Americans develop the condition each year. Epilepsy is the most prevalent disabling neurological disorder
across the life span, and is not controlled by medications in more than one-third of patients. Epilepsy surgery is
an accepted treatment. Developments in minimally extensive surgical resections and more recently minimally
invasive brain stimulation strategies, require as a prerequisite accurate localization of the epileptogenic zone the network of abnormally behaving neurons -, which frequently extends beyond the margins of an abnormality
on an MRI in lesional epilepsy and may be challenging to delineate in non-lesional epilepsy. Pre-surgical
exploratory techniques – including imaging – have improved and allowed a better selection of surgical
candidates, however challenges in outlining the Epileptogenic Zone, the neural plasticity and propagation
pathways in epilepsy are still numerous.
The main goal of epilepsy surgery is to achieve seizure freedom without major side effects. This involves
appropriate clinical assessment, accurate localization of the origin of seizures, and detection of a focal
abnormality of the brain. Developing non-invasive accurate methods of studying epilepsy patients would
dramatically improve their medical care and decrease associated surgical complications. Non-invasive imaging
techniques, such PET (Positron emission tomography) are attractive because they allow imaging of
physiological and pathophysiological processes at the nanomolar level and in real time.
Experimental observations lead us to believe that Glutamate receptor modulatory changes as well as neuroinflammation may play a significant role in epileptogenesis.
The Glutamate system has been implicated in many epileptogenesis models, however much more research is
necessary to understand the involvement of these different receptors. TSPO’s (Translocator Proteins) are
mitochondrial proteins found in the brain and peripheral tissues. A variety of inflammatory stimuli induce
TSPO expression mostly in microglia. Increased TSPO expression has been described after brain injury or
neuro-inflammation associated with microglial activation, such as occurs with the neuronal damage that
accompanies several neurodegenerative diseases, including epilepsy. We propose to non-invasively image
neuro-inflammation in epilepsy patients with a specific TSPO radioligand [11C] PBR28 and Glutamate receptor
density with [18F] FPEB a specific mGluR5 Glutamate receptor PET probe.
Non-invasive clinical imaging of these two processes in epilepsy patients will hopefully give us a better
understanding of intricate processes driving epileptogenesis, better delineate the Epileptogenic Zone and
ultimately allow us to better characterize surgical and medical treatment options in the epilepsy population.
Multimodality functional mapping of language: Comparison of available methods
Presenting author: Nicolas Gaspard
Collaborating authors: Hal Blumenfeld, Richard Bronen, R. Todd Constable, Robert Duckrow, Marla
Hamberger, Scott Winstanley, Gerwin Schalk, Ken Vives, Hitten Zaveri, Irina Goncharova, Dennis Spencer,
Lawrence Hirsch
The optimal goal of epilepsy surgery is to resect the seizure onset zone while preserving surrounding functional
brain tissue. To achieve this goal, one must be able to precisely delineate functional cortical areas such as
language areas. The current standard method for language mapping is electrocortical stimulation mapping.
However, ESM has several technical and practical limitations and may not be the best approach. Functional
MRI is increasingly used for hemispheric lateralization of language prior to epilepsy surgery but its ability to
precisely map language areas seems unsatisfactory. More recently, electrocorticographic detection of high
gamma band activation (ECoG HGA) has emerged as an efficient tool for brain functional mapping. In this
project, we will directly compare these three methods to determine which functional brain mapping technique is
the most practical and reliable, or which techniques should be combined. We will also gather preliminary data
regarding improvements that can be made to the ECoG HGA method, including real-time analysis with the
SIEGFRIED algorithm, and the use of higher density electrode arrays (contacts closer together for finer
mapping).
In addition, we will take advantage of this series to begin to directly investigate the role of the hippocampus in
language. It has been shown that despite thorough language mapping, hippocampal resection is associated with
post-operative visual language decline.
Altogether this work will gather data that will improve pre-surgical language mapping.
3-Dimensional color movies of intracranial EEG for localizing seizures
Presenting author: Mark Youngblood
Collaborating authors: Stephen Jhun, Pue Farooque, Jenna Ji Yeoun Yoo, Hyang-Woon Lee, Irina
Goncharova, Xiao Han, Kenneth Vives, Dennis Spencer, Lawrence Hirsch, Hitten Zaveri, Hal Blumenfeld
Intracranial Electroencephalography (icEEG) is a common technique for preoperative localization of seizure
onset regions. While traditional analysis of icEEG information is effective in detecting familiar seizure onset
patterns, much potential exists for computational analysis of acquired data. Our lab has recently developed a
novel visualization tool to assist neurologists and other health professionals in understanding the spatial timecourse of seizure propagation. Using traditional icEEG data, electrode power is mapped onto a MRI-based, 3dimensional rendering of a patient’s cortex. Areas adjacent to each electrode are colored according to power
intensity and the data is filtered based on frequency and amplitude. Frames are generated for every one second
of icEEG data and compiled together to create a 3-dimensional color movie for review by clinicians. Insight
gained from this method of visualization could lead to increased accuracy during diagnosis and more effective
treatment for patients with Epilepsy.
Neural mechanisms of visual and auditory awareness: Searching for common ground
Presenting author: Leisel Martin
Collaborating authors: Ryan Aronberg, Jennifer Guo, Michael Crowley, Linda Mayes, R. Todd Constable,
Andrew Engell, Gregory McCarthy, Hal Blumenfeld
The neural mechanisms of perceptual awareness have been studied extensively in the past two decades, thanks
to advances in electrophysiology and neuroimaging, raising many questions about how and where sensory
awareness arises in the brain. Does this form of consciousness arise in a localized or distributed network?
What is the role of primary and association cortices in awareness? How important are feedback loops and the
associated high frequency oscillations? Most often, these questions have been explored using the visual system
as a model circuit. However, if a truly universal mechanism of awareness exists, then it would span other
sensory modalities.
With these questions in mind, we have designed a multimodal sensory task to examine perceptual awareness in
two sensory modalities simultaneously. Subjects are presented with brief, simultaneous, near threshold visual
and auditory stimuli. They are asked to pay attention to one stimulus or the other at the beginning of each trial,
and report on the side of its appearance (left or right) following the trial. They are also asked to report if they
heard and/or saw the stimuli. By modulating their attention randomly to one stimuli or the other, we hope to
dissociate attention from awareness in the analysis - a traditionally tricky proposition for studies of awareness.
The goal in designing this behavioral task is to then obtain simultaneous physiological data during intracranial
EEG and/or fMRI measurements. An event-related analysis will reveal whether activity in certain regions,
coupling between regions, or specific oscillatory frequencies corresponded to visual awareness, auditory
awareness, or both.
We expect that being able to record within-subjects data will allow for a maximally controlled comparison
across sensory systems. By utilizing a task in which simultaneous auditory and visual stimuli are presented, we
will search for common (or unique) mechanisms of perceptual awareness.
Expansion of intracranial electrode arrays at a single institution: Evidence for
epileptogenic networks
Presenting author: Willard S. Kasoff
Collaborating authors: Hitten P. Zaveri, Robert B. Duckrow, Lawrence J. Hirsch, Kenneth P. Vives, Susan S.
Spencer, Dennis D. Spencer
Rationale: The number and density of electrode contacts needed to adequately sample the epileptic brain is
unknown, but is likely far higher than currently-available technology can support. Furthermore, emerging
evidence supports the presence of widespread, often well-defined epileptogenic networks that extend far beyond
the focal abnormalities seen on non-invasive tests of localization-related epilepsy (LRE). Together, these
observations suggest that intracranial EEG (icEEG) recordings that are focused only on areas of structural or
metabolic abnormality – as commonly designed at most epilepsy centers – may under-sample a given patient’s
epileptogenic network and provide false localization of seizure onset. Accordingly, our practice in the Yale
Epilepsy Surgery Program (YESP) has been one of increasingly broad icEEG coverage in the evaluation of
most forms of LRE. Here we quantify and evaluate that practice over the past 20 years.
Methods: We retrospectively reviewed our prospectively-collected database of patients monitored with icEEG
in the YESP since 1990. The number of icEEG contacts placed per patient, results of intracranial
monitoring and surgical outcomes were abstracted and analyzed with descriptive statistics.
Results: We observed a steady increase in the number of icEEG contacts over the study period, with average
numbers of contacts rising from 80-100 per patient in the early 1990s to 200 per patient in the mid-2000s. This
trend has continued in recent years as our technical capabilities have increased. Although overall rates of
surgical resection and outcomes have remained stable, we have frequently observed network phenomena that
would not have been detected by icEEG studies directed only to the areas of abnormality seen on noninvasive
testing. A small number of patients developed neurologic symptoms possibly due to electrode mass effect,
leading us to adopt a strategy of broad survey icEEG studies followed by more focused pre-resection studies.
Conclusion: Intuition that LRE often represents a network process, in which the visible abnormality is only the
“tip of the iceberg” of functionally-connected epileptogenic tissue, led our program to use broader arrays of
subdural electrodes over the past two decades. These arrays have in turn produced more evidence of network
phenomena, including the characterization of a few well-defined epileptogenic networks. We have been limited
by technical constraints, including the number of available recording channels, and the contact density and mass
effect of currently-available electrode arrays. These constraints highlight the need for new materials for
electrode fabrication, increased transmission capabilities, and new computational approaches to the
temporospatial analysis of large numbers of icEEG channels.
We believe that broad icEEG monitoring is needed to fully understand most cases of LRE. Ultimately,
understanding epileptogenic networks in patients with LRE may lead to treatment strategies aimed at
disconnection or disruption of epileptogenic networks in cases not amenable to focal resection.
A possible lack of intracranial EEG support for a resting state network observed with
fMRI
Presenting author: Dominique Duncan
Collaborating authors: Robert Duckrow, Steven Pincus, Irina Goncharova, Lawrence Hirsch, Dennis Spencer,
Ronald Coifman, Hitten Zaveri
Rationale: We tested if a relationship between distant parts of the default mode network (DMN), a resting state
network (RSN) defined by fMRI studies, can be observed with intracranial EEG (icEEG) recorded from patients
with localization-related epilepsy.
Methods: This study was performed on 9 patients being evaluated for possible epilepsy surgery. Three timeseries relationship measures: magnitude squared coherence (MSC; measured for delta, theta, alpha, beta,
gamma, and a high frequency band), mutual information (MI), and cross-approximate entropy (cross-ApEn),
were estimated from continuous icEEG recordings from two test areas within the RSN denoted (T1, T2) and
one control area outside of the RSN denoted (C). While MSC measures primarily linear relationships, MI and
cross-ApEn quantify both linear and non-linear relationships. We tested if the relationship between T1 and T2
was stronger than the relationship between each of these areas and C, the control area.
Results: Measured with MSC, MI, and cross-ApEn, the relationships between the two test areas T1 and T2,
which were part of the studied RSN, showed very significant (non-zero) association but were not stronger than
the relationship between each of the two test areas and the control area.
Conclusions: We did not observe enhanced relationships in icEEG measurements between areas of a fMRI
defined RSN suggesting one of the following possibilities: (1) the difference in activities measured by fMRI and
icEEG precludes the observation of this relationship with icEEG, (2) the setting within which our observations
were made interferes with the observation of this relationship, or (3) that this RSN does not exist in patients
with localization-related epilepsy.
Nasal midazolam as a seizure-aborting therapy and comparison with oral and rectal
benzodiazepines in adults
Presenting author: Alexandra Svoronos
Collaborating authors: Madeline Nocero, Hiba Arif, Stanley Resor Jr, Lawrence Hirsch
Objective: To evaluate patient experience with home use of nasal midazolam (nMDZ) for acute seizures and
compare to rectal diazepam (rDZP) and oral benzodiazepine (oBNZ) use.
Background: The only FDA-approved home treatment for acute seizures is rDZP; oBNZ are also commonly
used. Recently nMDZ has been studied because it may be more rapid and convenient.
Design/Methods: We reviewed charts of 45 adults with epilepsy who had been prescribed nMDZ (off-label,
using IV solution administered via metered-dose nasal sprayer) by their epileptologist and used it at least once.
Patients/caregivers were given a questionnaire to retrospectively assess efficacy, tolerability, convenience,
comfort and overall satisfaction with nMDZ in aborting seizures or seizure clusters, and to compare it to rDZP
and oBNZ. Paired t-tests, Wilcoxon signed-rank tests, and Fisher’s exact tests were used for analysis.
Results: 33 patients (73%) returned the questionnaire. 79% found nMDZ effective in controlling seizures.
Median time to seizure cessation for nMDZ/rDZP/oBNZ was 1.5/3.5/9 min; in those who had used both,
seizures stopped faster with nMDZ versus oBNZ (p=0.08). Median time to recovering full function was
10/19/43 minutes, and among those who had tried two formulations, recovery was faster with nMDZ than with
rDZP or oBNZ (p<0.05 for both). Median discomfort during use was 2/4/1 out of 10 (10 the worst), and median
social embarrassment was 1/9/1. Patients were more likely to participate in activities outside the home with
access to nMDZ versus rDZP (72% vs 14%; p<0.01). Six of seven patients preferred nMDZ over rDZP. No
serious adverse events were reported with any formulation.
Conclusions: nMDZ is an effective and rapidly-acting treatment for acute seizures that has a positive effect on
patient quality of life. Patients prefer nMDZ over rDZP, and time to effect is faster than with oBNZ. Time to
return to normal is much faster with nMDZ than the other two routes.
Brain stimulation for epilepsy: Update on responsive neurostimulation and deep brain
stimulation
Presenting author: Robert D. Duckrow
Collaborating author: Lawrence J. Hirsch
Electrical stimulation of the brain to map or alter function has a historical tradition at Yale as a method of
physiological investigation exploited most notably by Fulton and Delgado. In our era it has gained prominence
as a therapeutic tool shown to be safe and effective when applied to Parkinson disease and essential tremor.
More recently, electrical stimulation of the brain has been tested as a treatment of medically intractable
epilepsy. It has been applied continuously to deep brain structures to modulate excitability or intermittently to
target the source of epileptiform discharges. Since 2002 our Epilepsy Program has participated in multi-center
trials of a medical device that delivers responsive electrical stimulation directly to seizure onset regions not
amenable to surgical resection. Yale contributed 4 subjects to the pivotal prospective double-blind study of
device effectiveness. This trial is now complete with 191 subjects enrolled through 32 study centers. The
responsive neurostimulator system was found to be safe and effective, providing a 38% reduction in seizure
frequency. The results of this trial will be reviewed and compared with a recent trial of continuous stimulation
of the anterior nucleus of the thalamus as an alternative therapy for medically intractable epilepsy.
Driving safety evaluation on the inpatient epilepsy monitoring unit
Presenting author: Andrew Bauerschmidt
Collaborating authors: Mark Youngblood, Stephen Jhun, Zachary Kratochvil, Cel Ezeani, Louis Manganas,
Jenna Ji Yeoun Yoo, Yan Zhang, Robert B. Duckrow, Richard Mattson, Jullie Pan, Kamil Detyniecki, Pue
Farooque, Hamada Hamid, Susan Levy, Francine Testa, Lawrence Hirsch, Hal Blumenfeld
Epileptic seizures frequently involve loss of consciousness, impaired motor control, and an impaired ability to
interact with one’s environment. Just such capacities are required for the task of driving a car, a common yet
cognitively complex task. As a result, patients with epilepsy are at increased risk of serious automobile
accidents and are often explicitly restricted from driving, regardless of the nature of their individual seizures.
Clinical assessment for driving risk is currently non-standardized and highly subjective. Almost all data
regarding risk factors for driving is retrospective and often anecdotal in nature. Here we describe our ongoing
prospective study in which objective data about driving performance is collected in patients experiencing
epileptic seizures. We utilize a previously established driving simulation task coupled with continuous
audio/video/EEG acquisition. Driving performance metrics collected during all interictal periods is used to
compute a probability distribution of normal driving performance. Identical data collected during the ictal
period is used to calculate deviation in performance for each metric during the observed time window of
epileptic activity. The result is a quantitative description of altered (or preserved) driving ability in reference to
a patient’s own driving baseline, as well as a likelihood statistic of such deviation being correlated to the seizure
window. This data will be used to categorize different types of impairment that result from different types of
seizures, and those with different anatomic origins.
Clinical assessment for driving risk must ultimately result in a go or no-go decision in the form of the guidance
a neurologist gives to refrain from driving or not. While some seizures are very severe and clearly inhibit
driving, some result in a very brief or questionably significant degree of impairment. This data-driven analysis
should provide a more sensitive and objective basis for identifying and describing impairment in such seizures.
Executive functioning in temporal lobe epilepsy patients with right and left mesial
temporal sclerosis
Presenting author: F. Scott Winstanley
Collaborating authors: Shelly Komondoros, Sarah Strube, Jagriti Arora, Hyang Woon Lee, Dennis D. Spencer,
R. Todd Constable. Departments of Neurology, Diagnostic Radiology, Neurosurgery, and Biomedical
Engineering, Yale University School of Medicine; Department of Neurology, Ewha Womans University School
of Medicine and Ewha Medical Research Institute, Seoul, Korea
Rationale: The relationship between memory abilities and hippocampal integrity has been well demonstrated in
the neuropsychological literature, specifically, in patients with temporal lobe epilepsy. Individuals with TLE,
specifically MTS, consistently demonstrate poor performance on tests of memory. Less understood is emerging
evidence between focal TLE with MTS and executive functioning (traditionally viewed as “frontal lobe”
cognitive activities). This is the first of a two part study that seeks to better understand 1) cognitive abilities
beyond memory functioning in patients with TLE, particularly in the domain of executive functioning, and 2)
functional connectivity of neural-anatomical networks in these patients.
Methods: We recruited 29 TLE patients who performed both resting state fMRI and neuropsychological tests as
part of presurgical evaluations, and underwent standard temporal lobectomy with at least one year of
postoperative follow-up. There were 15 left and 14 right TLE patients, with mean age at surgery of 39.1 ± 11.1
years old. All patients underwent preoperative neuropsychological testing which included tests of verbal and
non-verbal memory functioning, as well as one or more tests of executive functioning (e.g. WCST, Trails B,
Stroop Test).
Results: When combining the two groups (L-TLE and R-TLE), approximately 45% of the sample showed
deficits on at least one test of executive functioning. Further analysis of within group deficits showed that, of
the 15 left TLE patients, approximately 46% had impairment on one or more tests of executive functioning, and
43% of right TLE patients had impairment on one or more tests of executive functioning. A number of patients
also showed postoperative decline on tests of executive functioning.
Conclusions: These findings suggest that cognitive impairment in TLE patients with MTS extend beyond
material specific memory domain, and that a number of patients also have deficits in executive functioning.
This is consistent with previous studies that demonstrated different “cognitive phenotypes” in patients with
temporal lobe epilepsy. Further research examining functional connectivity between frontal and temporal lobes,
as well as examining potential secondary frontal lobe dysfunction, will be beneficial in explaining the reason for
such elevated levels of executive dysfunction in focal TLE patients. This research is currently ongoing in our
laboratory.
Neural correlates of cognitive abnormality in temporal lobe epilepsy: Evidence from fMRI
intrinsic connectivity analysis
Presenting author: F. Scott Winstanley
Collaborating authors: R. Todd Constable, Jagriti Arora, Dennis D. Spencer, Hyang Woon Lee. Departments of
Neurology, Diagnostic Radiology, Neurosurgery, and Biomedical Engineering, Yale University School of
Medicine; Department of Neurology, Ewha Womans University School of Medicine and Ewha Medical
Research Institute, Seoul, Korea
Rationale: Voxel based analyses of resting-state fMRI BOLD signal fluctuations can provide useful information
regarding large-scale, spatial patterns of intrinsic activity throughout the brain including regions critical for
important cognitive functions, such as memory and language. Such measures of intrinsic connectivity contrast
(ICC) provide information on how well connected, functionally, any given tissue element is and can provide a
means of investigating the relationship between ICC and cognitive function. This study aims to elucidate the
neural correlates of cognitive impairment in epilepsy by analyzing the ICC in intractable TLE patients. We
hypothesized that ICC would demonstrate local changes in functional connectivity associated with changes in
psychological test scores across subjects.
Methods: fMRI-ICC was calculated for 25 temporal lobectomy patients (12 left, 13 right). In this work, ICC
was calculated using the network measure, degree, on a voxel basis, which reflects the number of other voxels
that particular voxel is connected to with a correlation coefficient of the resting-state voxel timecourse great
than 0.25. ICC was conducted for the whole-brain, an extended medial temporal mask, and a limited
(hippocampus only) mask, for ipsi- (which measures only those connections within the hemisphere), and contra(which measures only those connections to the opposite hemisphere) degree measures. These ICC measures
were then correlated with preoperative neuropsychological test scores.
Results: Verbal SRT scores were positively correlated with ipsi-ICC in left hippocampus and contra-ICC in
both hippocampi using medial temporal mask. Verbal SRT showed similar positive correlation with ipsi- and
contra-ICC values with the whole brain mask in left middle and part of inferior temporal gyri. Impaired nonverbal SRT was correlated with decreased ipsi- and contra-ICC in right hippocampus, right superior temporal
gyrus with medial/lateral temporal mask. BNT showed similar positive correlation with left superior/middle
temporal gyri.
Conclusion: These findings suggest that impairments in cognitive function in TLE patients are reflected in the
intrinsic functional organization of the brain as measured by ICC. Impairments of verbal learning and naming in
TLE patients showed alterations in dominant temporal lobe structures while non-verbal learning abnormalities
were closely related to ICC changes in non-dominant temporal structures, in good agreement with the previous
knowledge of memory and language networks.
Potential genetic etiologies for Rasmussen's encephalitis
Presenting author: Boel Brynedal
Collaborating authors: Margarita Dominguez Villar, Chris Cotsapas
Rasmussen’s encephalitis is a chronic progressive unilateral inflammation of the brain of uncertain aetiology,
characterized clinically by intractable focal epilepsy, progressive hemiparesis and cognitive decline. The disease
is rare, affecting approximately 1 in 500,000 live births. Only epilepsy surgery, specifically a functional or
anatomical hemispherectomy (disconnection or complete resection of the affected brain hemisphere), will halt
the symptoms of the disease.
Anecdotal reports indicate autoimmune disease burden in parents of cases; these diseases are known to have a
shared, genetic basis for risk. This suggests that genetic variation may predispose to RE. We have recently
uncovered two pairs of distantly related RE cases, one each in the US and UK. A common genetic risk factor is
a likely explanation for the occurrence of RE in distant relatives.
Our hypothesis is that mutations inherited by related cases from their common ancestor will predispose to RE.
We are using genome-wide genotyping and exome resequencing to (i) identify such genomic regions and (ii)
identify functional, coding mutations in genes in those regions, which will be good causal candidates. We hope
to uncover a gene or genes that predispose to RE risk; this will provide biological clues about pathogenesis that
will help development of treatments and/or diagnostics.
Exploring the seizure network in a novel animal model of temporal lobe epilepsy
Presenting author: Ronnie Dhaher
Collaborating authors: Helen Wang, Argyle Bumanglag, Hitten Zaveri, Tore Eid
Rationale: Mesial Temporal Lobe Epilepsy (MTLE) is one of the most common forms of drug-resistant,
localization related epilepsy in humans. We recently developed a model of MTLE by chronic infusion of the
glutamate synthesis inhibitor Methionine Sulfoximine (MSO) unilaterally into the hippocampus of rats. In the
present study, we worked to improve the MSO model by determining the effect of injection location in the
hippocampal formation on (1) total number of seizures over 21 days, (2) duration of seizures, and (3) % time in
Racine stage 1-5.
Methods: Male Sprague Dawley rats weighing between 330-400 g were implanted with an osmotic pump
injecting MSO into the right hippocampal formation at a rate of 0.25 µl/hr. Different groups of rats were
injected into (1) the dentate granule cells (n=7), (2) subiculum/pyramidal cells (n=4), (3) subiculum/molecular
layer (n=4), and (4) CA1 (n=3). In addition to these brain regions, injections were also made into the lateral
ventricle (n=6). Intracranial EEG activity was monitored from above the neocortex overlying the dorsal
hippocampal formation for a continuous period of 21 days. EEG analysis was correlated with simultaneous
video recordings to determine the stage of seizure according to the Racine scale.
Results: Rats injected with MSO into the CA1 showed significantly higher number of seizures than all other
groups during the first day following surgery (p<0.01). Rats that received MSO injections into the lateral
ventricle showed significantly less seizures over a 21 day period than rats that received injections into the
dentate gyrus (p=0.02), and showed significantly shorter seizure durations (~40 s) than rats in all other
hippocampal formation groups (~90 s) (p<0.01).
Conclusion: These results may have implications for improving the MSO model, leading to a better
understanding of the mechanisms underlying mesial temporal lobe seizures, and thus development of
therapeutic treatment for MTLE.
Magnetic resonance spectroscopy identifies neural progenitor cells in the live human
brain
Presenting author: Louis Manganas
Collaborating authors: Zhang X, Li Y, Hazel RD, Smith SD, Wagshul ME, Henn F, Benveniste H, Djuric PM,
Enikolopov G, Maletic-Savatic M
The identification of neural stem and progenitor cells (NPCs) by in vivo brain imaging could have important
implications for diagnostic, prognostic, and therapeutic purposes. We describe a metabolic biomarker for the
detection and quantification of NPCs in the human brain in vivo. We used proton nuclear magnetic resonance
spectroscopy to identify and characterize a biomarker in which NPCs are enriched and demonstrated its use as a
reference for monitoring neurogenesis. To detect low concentrations of NPCs in vivo, we developed a signal
processing method that enabled the use of magnetic resonance spectroscopy for the analysis of the NPC
biomarker in both the rodent brain and the hippocampus of live humans. Our findings thus open the possibility
of investigating the role of NPCs and neurogenesis in a wide variety of human brain disorders.
SLIDE PRESENTATIONS
Thursday, October 27th
Session I: Imaging
Metabolic imaging at high field: Detection of neuronal injury and dysfunction
Presenting author: Hoby Hetherington
Collaborating authors: Veronica Chiang, Kenneth Vives, Nihal de Lanerolle, Dennis Spencer, Jullie Pan.
Departments of Neurosurgery, Diagnostic Radiology, and Neurology, Yale University School of Medicine
Magnetic Resonance Spectroscopic Imaging (MRSI) is a valuable tool in evaluating neuronal injury and
dysfunction in a variety of pathologies including epilepsy, trauma and brain tumors. Measurements of N-acetyl
aspartate (NAA), creatine (Cr) and choline (Ch) by 1H MRSI have demonstrated substantial alterations in these
patient groups. In epilepsy, reductions in NAA can be used as markers of neuronal impairment and are
correlated with cognitive function and EEG changes. Further, in temporal lobe epilepsy, these changes manifest
themselves as a network of correlated injury involving the hippocampi, thalami and basal ganglia. Additionally,
in animal models of epileptogenesis, NAA levels decrease prior to the onset of spontaneous seizures; and occur
in the absence of significant neuronal loss. Conversely, in patients with positive surgical outcomes, contralateral
NAA levels recover following surgery. In brain trauma patients experiencing clinical symptom (soldiers
exposed to blast and professional athletes with multiple concussive events), reductions in NAA and elevations
in Ch (likely reflecting axonal injury) are seen despite normal MRIs. In subjects with memory impairment
arising from blast exposure, these alterations localize to the hippocampi. In patients with brain tumors,
successful treatment with radiosurgery results in the recovery of NAA from regions about the tumor. Thus
measures of NAA provide a sensitive means for detecting neuronal injury and dysfunction in a broad range of
pathologies. In addition to these measures of neuronal impairment and loss, 1H MRSI can also provide
measures of the intracellular concentrations of key neurotransmitters including glutamate, glutamine and
GABA, which can be used to characterize alterations in brain neurotransmitter metabolism to various antiepileptics such as topiramate, lamotrigine, gabapentin and valproate.
Networks in epilepsy: A factor analysis in MTLE
Presenting author: Jullie Pan
Collaborating authors: DD Spencer, RI Kuzniecky, R Duckrow, HP Hetherington, SS Spencer. Departments of
Neurosurgery, Neurology, and Radiology, Yale University School of Medicine; Department of Neurology, NYU
School of Medicine
The concept of an epileptic network has long been suggested from both animal and human studies of epilepsy.
Given the metabolically costly nature of seizures we have hypothesized that the network can be detected via use
of MR spectroscopic imaging, in particular with the measurement of NAA/Cr. NAA/Cr has been shown by
many groups to be sensitive to neuronal function and injury. Our group has developed and implemented such
measurements at ultra-high field (4 and 7Tesla) to better understand the pathophysiology of epilepsy, in
particular localization related epilepsy which may be of practical interest for localization. In this report we use a
multivariate common factor analysis to evaluate the limbic system in MTLE and control. This multivariate
analysis is performed with data from the bilateral hippocampi, thalami, basal ganglia and insula. We extract two
major factors that explain the data’s variability in control and MTLE patients. In controls, these factors
characterize “thalamic” and “subcortical language” functions. The MTLE patients also exhibit a “thalamic”
factor, but show a second factor involving the bilateral basal ganglia and ipsilateral insula. As a network of
metabolic dysfunction, we hypothesize that these relationships characterize a subcortical seizure network to be
interpreted in the context of seizure propagation. We show data from a linear discriminant analysis evaluating
the presence or absence of the limbic network in n=12 neocortical epilepsy patients. We have also implemented
these MR spectroscopic imaging approaches in a broader context for neocortical epilepsy, and demonstrate
ongoing work at 7T.
Methods for tract-based quantification of white matter from DTI
Presenting author: Larry Staib
Collaborating authors: Gary Ho, Fei Wang, Hilary Blumberg, Xenios Papademetris
White matter has been implicated in the pathophysiology of epilepsy and diffusion tensor imaging (DTI) can be
used to quantify white matter alterations which may be present. Parcellation of white matter into tracts can aid
in the understanding of these differences. Most existing methods for parcellation from DTI use fiber tracking
and bundling to integrate individual tractography-based curves and group them together based on shape and
location. These methods suffer from image noise and cumulative tracking errors. Quantitative comparison is
also not straightforward. To simplify the process and offer standardized white matter samples for analysis, we
have developed a new integrated fascicle parcellation and normalization method that combines a generic
parametrized volumetric tract model with orientation information from diffusion images. The resulting tract
boundaries are computed interactively and allow tract-specific diffusion parameters and structural information
to be quantified. The new technique also offers a tract-derived spatial parametrization for each voxel within the
model. Cross-subject regional comparisons can be computed based on these parameters.
EEG, fMRI, and behavior in childhood absence epilepsy
Presenting author: Jennifer Guo
Collaborating authors: Xiaoxiao Bai, Stephen Jhun, Wendy Xiao, Michael Wang, Michiro Negishi, Linda
Mayes, Michael Crowley, R. Todd Constable, Hal Blumenfeld
Childhood absence epilepsy (CAE) is characterized by 3-4 Hz spike-and-wave discharges on
electroencephalography (EEG) and temporary loss of consciousness. Behavioral performance is sometimes
spared during absence seizures but can be highly variable. Furthermore, while absence seizures are considered
generalized events, previous studies show they commonly exhibit focal changes in attention network areas on
functional magnetic resonance imaging (fMRI). Areas involved during absence epilepsy include the
orbital/medial frontal cortex, medial/lateral parietal cortex, and thalamus. We hypothesize that EEG and fMRI
changes at these regions are related to the variable behavior observed during seizures. We performed
simultaneous EEG-fMRI in 24 patients while they performed a continuous performance task (CPT) or a
repetitive tapping task (RTT) to measure attentional vigilance. 240 seizures were captured, and EEG and fMRI
were analyzed and correlated to behavior. Seizures caused greater impaired performance during the more
difficult CPT compared to RTT. However, performance on both tasks showed inter-seizure and inter-patient
variability. Seizure duration was associated with degree of impairment. EEG time-frequency analysis
determined relationships between performance and power at discrete frequency bands. We demonstrate variable
spatial distribution of power changes in EEG signal across seizures and patients. Time course and amplitude of
fMRI signal changes were analyzed using statistical parametric mapping (SPM) and in-house software. A
dynamic sequence of ictal fMRI changes was observed in orbital frontal, parietal, and other cortical areas as
well as the thalamus. In one patient who had a large number of seizures in the scanner, greater frontal cortex
decreases were associated with poor task performance. Ongoing analyses are investigating possible changes in
network metrics in cortical and subcortical attention areas during seizures and their relation to variable task
performance. Establishing the relationship between behavior and EEG-fMRI signals will provide insight into
the mechanisms of loss of consciousness during absence seizures.
Novel approaches to measuring local neuronal injury and dysfunction
Presenting author: Todd Constable
Collaborating authors: Scott Winstanley, Hyang Woon Lee, Hal Blumenfeld, Jagriti Arora, Dennis Spencer
Resting-state functional magnetic resonance imaging has seen explosive growth in applications and interest in
the past 5 years and while the promise of this approach is high, there remain challenges to its widespread use in
both neuroscience based research, clinical research and in clinical applications. This talk will focus on the
application of network theory approaches to the analysis of resting-state fMRI data in epilepsy.
Task-induced and task-evoked electrophysiological responses from intracranial electrodes
and their relationship to functional MRI
Presenting author: Gregory McCarthy
Collaborating author: Andrew Engell
The presentation of a visual stimulus such as checkerboard pattern, face, word, or object evokes complex
changes in the EEG recorded from electrodes in occipital and occipitotemporal cortex. These changes can be
characterized as those that are time-locked to the stimulus, and those that reflect non-time-locked (or phaselocked) changes in oscillatory or rhythmic potentials. It is common to refer to time-locked potentials are being
evoked by the stimulus, while changes in oscillatory potentials are described as being induced by the stimulus.
We have been studying the properties of potentials evoked and induced by simple visual stimuli, such as
checkerboard patterns, and more complex visual stimuli, such as faces in a large sample of patients with
implanted electrodes. We have also compared the pattern of these responses to functional MRI studies using the
same stimuli. Our results suggest that the fMRI response more closely reflects induced oscillatory potentials
than evoked potentials for these visual stimuli.
Session II: Clinical/Electrophysiology
Psychiatric comorbidity and seizure outcome
Presenting author: Hamada Hamid
Collaborating authors: Hilary Blumberg, Hal Blumenfeld, James Dziura
People with epilepsy are reported to have up to 6-12 times greater risk of suicide than the general population.
While most patients experience long-term improvement in mood and anxiety symptoms with better seizure
control, both medical and surgical interventions that are successful at lowering seizure frequency can worsen
depressive symptoms and suicidality. For many people with epilepsy, depression affects quality of life
independent of seizure frequency. Therefore, depression in epilepsy does not appear to be simply a reaction to
the burden of seizures but appears to have a neurobiological basis. Understanding the pathophysiology of
mental illness in epilepsy is critical in improving quality of life and developing targeted treatment, and may also
help elucidate the underlying neurobiology of depression disorders and suicidality in general. Frontal and
temporal lobe changes have been associated with both epilepsy as well as primary mood disorders, emotional
dysregulation, and suicidality.
Our program continues to collaborate with Dr. Hilary Blumberg and the Yale Mood Disorders Research
Program in studying white matter connections of people with epilepsy and depression using Magnetic
Resonance Diffusion Tensor Imaging. Furthermore, we continue to analyze the role of anxiety and mood
disorders in surgery outcome from the Multicenter Study of Epilepsy Surgery, the largest epilepsy surgery
outcome cohort.
The Yale Epilepsy Program and its collaborators have many opportunities to expand research in the
neuropsychiatry of epilepsy. Given the large volume of epilepsy surgery, advanced neuroimaging and in vivo
microdialysis techniques may be used to further explore the neurobiology of epilepsy and neuropsychiatric comorbidity. For instance, Dr. Idil Cavus has presented preliminary evidence that increased extracellular
glutamate is associated with increased depressive symptoms. Drs. Julie Pan and Hoby Hetherington have
developed techniques to measure neurotransmitters such as glutamate and gama-aminobutyric acid (GABA)
using 7-Tesla Magetic Resonance Spectroscopy (MRS). Psychometric scales may be administered in epilepsy
surgery candidates prior to MRS studies. Finally, large-scale epidemiologic research may also be conducted
using the Veterans Administration (VA) national database, as Dr. Hamada Hamid is now a member of the VA
National Epilepsy Center of Excellence Research Workgroup.
Patient awareness of seizures
Presenting author: Kamil Detyniecki
Collaborating authors: Cel Ezeani, Andrew Bauerschmidt, Louis Manganas, Jenna Ji Yeoun Yoo, Yan Zhang,
Robert B. Duckrow, Richard Mattson, Jullie Pan, Pue Farooque, Hamada Hamid, Susan Levy, Francine Testa,
Lawrence Hirsch, Hal Blumenfeld
Our goal was to use behavioral testing to determine if deficits in memory and consciousness have any
association with underreporting of seizures; relate these deficits to seizure type and anatomical site of onset.
Patients undergoing seizure evaluation in a VEEG monitoring unit were recruited. Patients’ responsiveness was
assessed by reviewing videos of their seizures. We compared objective data obtained through VEEG to 3 testing
instruments used to verify patients’ report of their seizures: 1. Admission questionnaire, 2. Patient seizure log,
3. Daily seizure questionnaire administered by research staff to determine awareness of any seizures that
occurred in the preceding 24 hours.
A total of 93 subjects were recruited to this study. We recorded 253 partial seizures comprising 38 secondary
GTC, 118 CPS, 43 SPS, and 54 where level of consciousness was not assessed. Patients were unaware of 54%
of all recorded seizures including 82% of GTC and 58% of CPS. In contrast, only 14% of all SPS were not
identified (p<0.001; chi-square test). Using logistic regression, we found that CPS were significantly less likely
to be recognized by patients compared to SPS (OR=0.17, 95% CI=0.05-0.55, p=0.003), and GTC were less
likely to be recognized compared to SPS (OR=0.02, 95% CI=0.01–0.10, p<0.001). No significant association
was found between preictal sleep vs. wake state and seizure awareness. In addition, we did not observe an effect
of side of seizure onset and seizure awareness.
This study demonstrates that patients are unaware of more than half of all recorded seizures during inpatient
VEEG monitoring. Seizures with impaired consciousness (CPS and GTC) were more likely to go unreported
suggesting that consciousness may be a factor influencing the ability of patients to recognize and accurately
report their seizures. Further study is needed to investigate the extent to which altered memory function or
language impairment contributes to seizure unawareness.
The antiepileptic drug database & CARET (computer assisted rational epilepsy therapy)
program
Presenting author: Alexandra Svoronos
Collaborating authors: Lawrence Hirsch, Richard Buchsbaum, Katie Dempsey, Celestine Ezeani, Hyunmi Choi
Objective: To determine the AED most likely to be effective in controlling seizures for each individual patient
with epilepsy.
Background: Approximately 40% of patients with epilepsy fail the first three medications they are started on,
and most require combination therapy. However, no randomized controlled trial can reveal the best AED
combinations or the AED that will most likely benefit an individual.
Design/Methods: The Antiepileptic Drug (AED) Database aims to compile demographic and treatment data of
patients with epilepsy seen on an outpatient basis in order to systematically determine the clinical utility of
AEDs, define therapeutic and toxic ranges for AEDs, and to analyze various combinations of AED regimens.
The computer-assisted rational epilepsy therapy (CARET) program will use data from the AED database to aid
healthcare providers in selecting regimens.
Studies: The following studies have been done in the past eight years: comparative effectiveness of AEDs in
older adults with epilepsy; comparison and predictors of patient-reported cognitive side effects of AEDs;
comparison of psychiatric side effect profiles of AEDs; comparison and predictors of rash associated with
AEDs; cross-sensitivity of skin rashes with AED use; correlating serum concentrations of lamotrigine with
tolerability. Some studies completed in the past year using the AED database: efficacy and incidence of visual
changes in long-term adult use of vigabatrin; efficacy, retention and tolerability of pregabalin, and comparison
to gabapentin; efficacy of rufinamide in adult patients with various refractory epilepsy syndromes; efficacy,
tolerability and clearance of lamotrigine in younger versus older adults.
Further Directions: The CARET program will take the characteristics of an individual (age, sex, epilepsy
syndrome, results of prior AED trials), match the patient with similar patients from the database, and report the
results as a list of all AEDs and the average 12 month retention in order. By clicking on each AED, you will get
a list of the exact frequency of all the side effects reported as well as rates of seizure freedom. This can be used
to help determine the best AED regimen for an individual patient. Patient preferences and weighting of the
significance of potential adverse events can be incorporated. Patients can be randomized to medical decision-
making using CARET vs not using it to see if AED choice differs and whether using CARET decreased adverse
effects, improved retention of the next AED chosen, and/or improved quality of life.
The metabolome of epileptic seizures in humans and animals
Presenting author: Tore Eid
Collaborating authors: Eyiyemisi Damisah, Dennis Spencer, Ronnie Dhaher, Argyle Bumanglag, Hitten Zaveri,
Kenneth Vives, William Wikoff, Elizabeth Canavan. Departments of Neurosurgery, Laboratory Medicine, and
Neurology, Yale University School of Medicine; Genome Center, University of California, Davis.
Up to one-third of individuals with epilepsy cannot control their seizures with current antiepileptic drugs, and
the available drugs have side effects that limit their use. Uncontrolled seizures are often disabling due to their
unpredictable appearance and frequently associated features such as loss of consciousness, physical injury and
social stigmatization. A method capable of predicting the occurrence of a seizure could dramatically improve
the way we treat seizures by moving away from long-term medication towards highly effective on-demand
therapies. This paradigm-changing approach to seizure treatment is likely to have a major impact on epilepsy
research and public health. However, no clinically useful method of seizure prediction is presently available.
This gap in knowledge is partly due to the nearly exclusive use of EEG recordings for seizure prediction and the
fact that the molecular mechanism of seizure generation remains largely unknown and cannot be understood by
EEG alone. In the present project we propose to use an unconventional but powerful combination of
intracranial EEG analysis, brain microdialysis and high-throughput chemical profiling (metabolomics) by mass
spectrometry, to reliably predict the occurrence of epileptic seizures. This approach is also expected to provide
important new information on the chemical mechanism of seizure generation, thereby facilitating the
development of more efficacious pharmacological treatments for epilepsy. Our central hypothesis is that
epileptic seizures have unique chemical signatures which include pre-seizure changes in endogenous chemicals
and metabolic pathways in the brain. We postulate that these changes can be exploited as predictive biomarkers
of and novel therapeutic targets for epileptic seizures. Our hypothesis is based on preliminary data from
patients with drug-resistant localization related epilepsies and from animal models.
Intracranial EEG in acute brain injury & multimodality monitoring of acute symptomatic
seizures
Presenting author: Lawrence J. Hirsch
Collaborating authors: Jan Claassen, Brandon Foreman, Bin Tu, Neeraj Badjatia, Allen Waziri, Sander
Connolly, Ronald G. Emerson, R. Morgan Stuart, J. Michael Schmidt, Kiwon Lee, Emily Gilmore, Stephan
Mayer
Patients with severe acute brain injuries are often monitored invasively with multiple devices including those
that measure intracranial pressure, brain tissue oxygen, cerebral blood flow (CBF), and multiple metabolites via
cerebral microdialysis. For the past few years, we also recorded intracortical EEG (ICE) in these patients
already undergoing invasive multimodality monitoring in order to help assess equivocal patterns on scalp EEG,
interpret sudden changes (e.g increased lactate) on microdialysis, and to act as a nearly artifact-free brain
monitor for ischemia, seizures and other acute brain events. A single “mini-depth” electrode was utilized (AdTech Spencer type, 8 contacts, 2.5 mm center to center) and was placed via a burr hole at the bedside; it was
placed superficially just through the cortical mantle in tissue at risk or the penumbra, and as close to the
microdialysis catheter as possible. In our first 14 patients, more than half had seizures detected on ICE, usually
with no scalp EEG correlate. Two patients had acute brain events (one ischemia from vasospasm, one
hemorrhagic conversion of an infarct) that were detected by ICE hours or more before any other method or
clinical exam. Some seizures showed changes on microdialysis and others did not. In some patients with
seizures or periodic discharges, there was an increase in CBF prior to seizures, and ictal patterns were
associated with an increase in brain temperature and decrease in tissue oxygen. ICE and multimodality
monitoring can detect acute brain events in real time that are not evident by other methods or exam, and allows
individualized, physiology-directed therapy to prevent or minimize neuronal injury.
Genetics of epilepsy
Presenting author: Murat Gunel
Abstract not available at time of printing
Spatial distribution of intracranially detected interictal spikes is related to the seizure
onset area
Presenting author: Irina Goncharova
Collaborating authors: Susan Spencer, Robert Duckrow, Lawrence Hirsch, Dennis Spencer, Hitten Zaveri
We have recently described a spatially distributed occurrence of interictal spikes in the hemisphere ipsilateral to
the seizure onset area. Here we examine if this distributed occurrence of spikes is related to the seizure onset
area.
A total of 71 consecutive patients were placed into 5 temporal (medial, MT, inferior, IT, inferomedial, MT-IT,
lateral, LT, and temporoparietal, LT-P) and 4 extratemporal (occipital, O, parietal, P, frontal F, and
frontoparietal, F-P) groups based on the location of the seizure onset. The tenth group consisted of unlocalized
patients, NL. Four 4-hour icEEG epochs, two from an on-AEDs period, one each from daytime and nighttime,
and two similar epochs from an off-AEDs period were analyzed. Spikes in the ipsilateral inferior temporal (IT),
lateral temporal (LT), occipital (O), parietal (P), and frontal (F) areas and in medial temporal structures (MT,
hippocampus and entorhinal cortex) were detected automatically and tabulated.
Interictal spikes occurred broadly throughout the ipsilateral hemisphere in most patients. Spike rates decreased
from the on-AEDs to the off-AEDs period, though the spatial distribution of spike rates did not differ between
these two time-periods (see Figure). A concordance between the area with the highest spike rate and the lobe of
seizure onset was observed only in approximately half of the patients (see Table). This result indicates that the
single brain lobe with the highest spike rate is not a good marker of the seizure onset area. The spatial
distribution of spike rates was different for the different seizure onset groups in all 4 epochs studied (p<0.0001,
chi-square), and could be used in pair-wise comparisons of patient groups to locate the seizure onset area, thus
supporting the hypothesis that the spatial distribution of interictal spike rates is related to seizure onset area.
Table. The single brain area with highest spike rate and its concordance with the seizure onset area for the
different patient groups studied. For each group, the number of patients where there was a concordance with the
seizure onset area is shown in bold.
Group (n)
On-AEDs Daytime Brain Area
Concor
dance
%
MT
IT LT O
P
MT (17)
35.3
IT (6)
F
On-AEDs Nighttime Brain Area
Concor
dance
%
MT IT LT O
P
7
3
1
47.1
50.0
3
2
1
MT-IT (5)
60.0
3
2
LT (6)
33.3
1
2
1
LT-P (5)
80.0
3
1
O (5)
60.0
P (6)
50.0
2
F (9)
55.6
1
F-P (5)
100.0
6
1
NL (7)
Total (64)
53.1
6
2
2
15
15
5
2
33.3
2
3
80.0
4
1
33.3
1
2
1
2
2
1
2
1
1
3
1
2
5
3
2
1
40.0
3
1
50.0
2
3
5
55.6
1
3
2
100.0
1
3
1
1
3
1
7
8
60.0
1
12
F
53.1
1
8
1
1
2
2
1
1
2
1
15
13
7
10
11
Figure. Spatial distribution of spike rates, averaged over all patients studied (n = 71) for the daytime and
nighttime epochs of the (a) on-AEDs and (b) off-AEDs periods.
SLIDE PRESENTATIONS
Friday, October 28th
Session III: Animal Models
Cortical and subcortical mechanisms of impaired consciousness in limbic seizures
Presenting author: Joshua Motelow
Collaborating authors: Abhijeet Gummadavelli, Robert Sachdev, Jason Cromer, Zaina Zayyad, Anne
Williamson, Asht Mishra, Basavaraju Sanganahalli, Fahmeed Hyder, Hal Blumenfeld
Focal seizure activity in the temporal lobe can cause loss of consciousness. The mechanism explaining this loss
of consciousness is not known. Temporal lobe seizures that cause loss of consciousness are associated with
slow oscillations across the neocortex. We recorded blood oxygen level dependent (BOLD) fMRI
measurements on a 9.4T system using a rodent model of complex-partial limbic seizures. Seizures were induced
by brief hippocampal stimulation with a pair of tungsten electrodes. FMRI signal increased in the hippocampus,
septal nuclei, and anterior hypothalamus and fMRI signal decreased in the neocortex, thalamus and midbrain
tegmentum. We measured multiunit activity and local field potential outside of the magnet to confirm that
BOLD increases indicated seizure propagation and BOLD decreases indicated reduced neuronal activity. The
anterior hypothalamus showed increased neuronal firing during seizures while the brainstem showed decreased
neuronal firing during seizures. The brainstem is a heterogeneous region containing cholinergic, GABAergic,
and glutamatergic neurons among other types. We recorded decreased firing from individual brainstem
cholinergic neurons during seizures labeled using the juxtacellular method. These findings suggest a mechanism
for ictal neocortical slowing in which (1) limbic structures such as the hippocampus, anterior hypothalamus and
septal nuclei are important seizure foci, (2) GABAergic projections of the lateral septum and anterior
hypothalamus actively inhibit the ascending arousal systems and (3) decreased neuronal activity in central
thalamic nuclei and the brainstem reticular formation leads to ictal slow waves in the neocortex. These results
suggest that BOLD measurements can be used to reliably map changing brain activity and to guide mechanistic
studies of impaired consciousness during limbic seizures.
Glutamine synthetase, astrocytes, and epilepsy: Mechanisms and novel therapeutic
approaches
Presenting author: Tore Eid
Collaborating authors: Ronnie Dhaher, Argyle Bumanglag, Clayton Haldeman, Eyiyemisi Damisah, Helen
Wang, Hitten Zaveri, Nihal de Lanerolle, Dennis Spencer, Mounira Banasr, Gerard Sanacora, Kevin Behar,
Fredrik Lauritzen, Linda Bergersen, Niels Danbolt. Departments of Laboratory Medicine, Neurosurgery,
Psychiatry, and Neurology, Yale University School of Medicine; Institute for Basic Medical Sciences,
University of Oslo, Norway
Prior studies have shown that the concentration of extracellular brain glutamate is markedly increased in areas
of seizure involvement in patients with localization-related epilepsies, especially temporal lobe epilepsy (TLE,
Cavus et al, Ann Neurol. 2005, 57:226-35). It has been postulated that the glutamate excess leads to
hyperexcitability and spontaneous recurrent seizures; however, the mechanism of the glutamate excess is not
fully understood. Here we provide evidence that a population of pathological astrocytes in the epileptogenic
hippocampal formation appears to be critically involved in the glutamate excess in TLE. These astrocytes are
characterized by: (a) loss of the glutamate degrading enzyme glutamine synthetase (Eid et al, Lancet 2004,
363:28-37), (b) increased concentration of intracellular (cytoplasmic) glutamate, (c) increased density of
aquaporin 4 on the plasma membrane with loss of perivascular accumulation of the protein (Eid et al., PNAS
2005, 102:1193-8), and (d) increased expression of monocarboxylate transporter 1 (Lauritzen et al., Neurobiol
Dis 2011, 41:577-84). We propose that the pathological astrocytes significantly contribute to the glutamate
excess, either by decreased uptake and metabolism of the amino acid, or by release of glutamate from the
astrocytes to the extracellular space. Studies are underway to further explore the validity of these mechanisms.
We are also investigating whether the pathological astrocytes can be converted to a normal phenotype using
gene therapy and cell therapy approaches. The expectation is that “repairing” pathological astrocytes will
represent a novel therapeutic approach for drug-resistant TLE by decreasing the extracellular brain glutamate
concentrations and preventing the occurrence of spontaneous seizures.
The Sloviter model
Presenting author: Nihal de Lanerolle
Collaborating authors: Alexander Li, Argyle Bumanglag
Research on the neuropathology of human temporal lobe epilepsy has made great strides in the last 20 years or
so. This work has radically transformed our appreciation of the complex nature of the molecular and
neuroanatomical changes in the hippocampus of patients with temporal lobe epilepsy associated with
hippocampal sclerosis. Broadly, two major pathological processes are evident. (1) Selective neuronal loss and
circuit reorganization in the dentate gyrus. (2) Hippocampal sclerosis with abnormal astrocytes, most prominent
in area CA 1. In comparing this pattern of pathology with currently widely used animal models of TLE, in
particular models using the chemoconvulsants Pilocarpine and Kainic Acid, it is evident that none of these
adequately resemble the human condition. Recently, Dr. Robert Sloviter and co-workers reported on some
newer models of TLE produced by specific patterns of perforant path stimulation. In two of these models – the
“30-30-8 model” and the “3 hr model”, in particular the former, the similarity of the neuropathological changes
is strikingly similar to the human hippocampus. The degree of injury is more restricted to the hippocampus and
changes in hippocampal neuronal circuit reorganization and astrocyte modification have similarities.
Additionally they have clearly defined latent periods between seizure initiation and recurrent seizure
development. Our laboratory has continued to develop these models to study the time course of the
development of pathological changes, especially changes during the latent period, in the formation of a
hippocampal seizure focus. We are also using them to test novel antiepileptic and neuroprotective drugs.
Evaluation of post-ictal respiratory and cardiac activity in centrally serotonin neuron
deficient mice
Presenting author: Gordon Buchanan
Collaborating authors: George Richerson. Department of Neurology, Yale University School of Medicine;
Veteran’s Affairs Medical Center, West Haven, CT; Departments of Neurology, Molecular Physiology, and
Biophysics, University of Iowa; Veteran’s Affairs Medical Center, Iowa City, IA
Sudden unexplained death in epilepsy (SUDEP) is a devastating condition in which epilepsy patients die for no
apparent reason with or without evidence of a recent seizure. Though this has been a long recognized syndrome,
quite little is known about the pathophysiology of this disease. Both cardiac and respiratory etiologies have
been proposed. Serotonin (5-HT) is a key regulator of breathing control. 5-HT dysfunction has been implicated
in the pathophysiology of SUDEP. Here we employ a mouse model in which nearly all 5-HT neurons have been
genetically deleted to determine whether 5-HT neuron absence contributes to seizure-related respiratory
dysfunction and death. EEG, EMG, EKG, body temperature, locomotor activity and breathing plethysmography
were recorded in wildtype (WT) mice and mice lacking 5-HT neurons (Lmx1bf/f/p) before, during and after
seizure induction via either graded pilocarpine treatments (50 mg/kg i.p. every 20 min until recurrent convulsive
seizures observed) or electroshock (10-50 mA, 0.2s, 60 Hz sine wave stimulation via ear electrodes). Lmx1bf/f/p
mice experienced seizures after lower doses of pilocarpine compared to WT. Lmx1bf/f/p mice also experienced
each Racine category of seizure at a shorter latency than WT. Invariably, Category 4 seizures progressed to
motor status epilepticus (SE) in all animals of both genotypes. In the post-ictal period following prolonged
seizures Lmx1bf/f/p mice display profound reduction of respiratory rate and irregularity of respiratory rhythm. All
Lmx1bf/f/p mice and most WT further progressed to death. Only WT mice in which SE resulted in death were
included in this analysis. The latency to death from time of first injection was shorter for Lmx1bf/f/p compared to
WT. Lmx1bf/f/p mice experienced electrically-induced seizures at lower stimulus intensity than WT. In both
genotypes, the tonic phase was accompanied by respiratory arrest. Normal breathing spontaneously resumed at
the onset of the clonic phase in WT. In the majority of Lmx1bf/f/p mice, however, breathing did not
spontaneously recover and the animals expired. Many Lmx1bf/f/p mice did not exhibit clonic activity. Following
attenuation of EEG signal and respiratory arrest resulting from pharmacologically- or electrically-induced
seizures, cardiac potentials could be recorded for up to 6 min. These results indicate that elimination of central
5-HT neurons renders mice more susceptible to seizure induction and more prone to seizure-related sudden
death. These data further indicate that respiratory mechanisms may be more directly responsible for death than
cardiac arrest and that the 5-HT neuron deficit is responsible for the post-ictal breathing abnormalities. These
findings may have important implications for SUDEP.
Where fMRI and electrophysiology agree to disagree: Corticothalamic and striatal
activity patterns in the WAG/Rij rat
Presenting author: Asht Mishra
Collaborating authors: DJ Ellens, U Schridde, JE Motelow, MJ Purcaro, MN DeSalvo, M Enev, BG
Sanganahalli, F Hyder, H Blumenfeld
The relationship between neuronal activity and hemodynamic changes under normal conditions and in
neurological disorders such as epilepsy it is commonly assumed that increased functional magnetic resonance
imaging (fMRI) signals reflect increased neuronal activity, and that fMRI decreases represent neuronal activity
decreases. Recent work suggests these assumptions usually hold true in the cerebral cortex. However, less is
known about the basis of fMRI signals from subcortical structures such as the thalamus and basal ganglia. We
performed fMRI studies with blood oxygen level dependent (BOLD) and cerebral blood volume (CBV)
contrasts at 9.4 Tesla; as well as laser Doppler cerebral blood flow (CBF), local field potential (LFP), and
multiunit activity (MUA) recordings in WAG/Rij rat model of human absence epilepsy. We found that during
spike-wave seizures, the somatosensory cortex and thalamus showed increased fMRI, CBV, CBF, LFP and
MUA signals. However, the caudate-putamen showed fMRI, CBV and CBF decreases despite increases in LFP
and MUA signals. These findings suggest that neuroimaging-related signals and electrophysiology tend to
agree in the cortex and thalamus, but disagree in the caudate-putamen. These opposite changes in vascular and
electrical activity indicate that caution should be applied when interpreting fMRI signals in both health and
disease from the caudate-putamen, as well as possibly from other subcortical structures.
GABAergic interneuron replacement in a mouse model of temporal lobe epilepsy
Presenting author: Janice Naegele
Collaborating authors: Xu Maisano, Stephanie Tagliatela, Sara Royston, Elizabeth Litvina, Mary Vallo,
Nicholas Woods, Ralph DiLeone, Gloster Aaron, Laura Grabel
Complex partial seizures arising from brain structures deep in the temporal lobes are one of the hallmarks of
Mesial Temporal Lobe Epilepsy (MTLE). Severe MTLE resulting from post-traumatic brain injury or
prolonged febrile seizures is often associated with hippocampal sclerosis, altered neurogenesis, and
neuroplasticity that contribute to hyperexcitability, seizures, and cognitive impairments. Because patients with
MTLE have difficulty controlling the seizures with conventional anti-epileptic medications, and surgical
removal of hippocampus can cause additional cognitive impairments, our research aims to develop novel fetal
stem cell-based therapy to replace injured neurons in the temporal lobes and suppress intractable seizures.
Working in mouse models of MTLE (kainic acid and pilocarpine models), we have shown that transplants of
fetal GABAergic progenitors can suppress spontaneous recurrent seizures. Limited availability of fetal brain
tissue makes this approach less desirable than using human embryonic stem cells (hESCs) or human induced
pluripotent stem cells (hIPS) to derive neurons. Our current work grafting ES cell derived GABAergic
progenitors into mice with MTLE indicates that over time, these cells survive, differentiate, and integrate into
the dentate gyrus in mice. The neurons express GABA and other molecules indicative of specialized
GABAergic interneuron types that are injured in MTLE. Many extend elaborate axonal arbors into the
molecular layer of the dentate gyrus. Functional analyses have also shown mature electrophysiological
properties similar to endogenous hippocampal interneurons. These studies provide a framework for evaluating
whether hippocamapl grafts of hES or hIPS cell-derived GABAergic interneurons has strong therapeutic
potential for severe forms of epilepsy for which alternative, less invasive approaches cannot be used.
Session IV: New Directions aka “Data Free Zone”
Genetics of common epilepsy
Presenting author: Chris Cotsapas
The last ten years of genome-wide genetics studies have revealed a multitude of risk loci to diseases across
psychiatry, neurology and beyond. Epilepsy has, comparatively, lagged behind the times. Recent efforts to
correct this are well underway and we are, I believe, poised to make significant discoveries which will provide
clues to the biology underlying epilepsy. I will provide an introduction to the genome-wide genetics field and
discuss ways in which I think the Yale Epilepsy Program can make substantive contributions to this field.
The future of viral vector therapy for epilepsy
Presenting author: Kenneth Vives
Collaborating authors: Nick Boulis, Scott McPhee, Jude Samulski, Thomas McCown
Gene therapy holds the promise of focally treating the abnormal tissue responsible for seizure generation in-situ.
The most promising means of introducing these new genes currently is through the stereotactic injection of viral
vectors. Research is currently moving forward in animal models looking at the safety and efficacy of delivering
GAD, adenosine, NPY, galanin and GDNF. The initial feasibility studies for delivering AAV2-GFP along the
longitudinal axis of the hippocampus of a non-human primate were successful and are reviewed here. This is
among the first steps towards application for a human clinical trial using this technique in patients with medial
temporal lobe epilepsy.
Solving SUDEP (sudden unexpected death in epilepsy)
Presenting author: Daniel Friedman
Collaborating authors: Lawrence Hirsch
Patients with epilepsy have a 2-3 fold increased risk of death compared to the general population. While injuries
associated with seizures, suicides, adverse effects of medications and the underlying etiology of the epilepsy
contribute to this increased mortality, sudden unexpected death in epilepsy (SUDEP) may be the leading cause
of death in patients with treatment-resistant epilepsy. SUDEP is defined as a sudden and unexpected nontraumatic or non-drowning-related death in a patient with epilepsy which may or may not be due to a recent
seizure. On autopsy, there is no evidence of anatomical or toxicological cause of death. Available evidence
suggests multiple potential mechanisms for SUDEP including seizure-related cardiac arrhythmias, post-ictal
apnea, and global shut down of cerebral function with loss of protective reflexes. The relative rarity of SUDEP
makes understanding the epidemiology and pathophysiology difficult. We are developing a registry for SUDEP
cases in the United States and Canada to collect a large repository of clinical, physiological, imaging, tissue,
and genetic data. This registry will serve to advance awareness of SUDEP among physicians (epileptology,
neurology, medical examiners) and lay individuals while also facilitating understanding the pathophysiology of
SUDEP. We seek to capture as many cases as possible through publicity campaigns that will include education
about SUDEP as well as awareness of the registry and the referral process by partnering with epilepsy
organizations. We will use a toll-free number that can be called at any time to enhance the ease of referrals.
Research coordinators would collect data from interviews with family members regarding the seizure history,
lifestyle factors, and circumstances of death. We would also obtain medical records, MRI images, EEGs, EKGs
and autopsy reports whenever available. We have partnered with existing SUDEP registries (e.g., Canadian
Pediatric SUDEP; MORTEMUS study of EMU-based SUDEPs) to share relevant data. The clinical,
physiological and tissue material deposited in the registry will be made available to investigators to generate
and test novel hypotheses about the pathophysiology of SUDEP.
Stimulus-induced rhythmic, periodic or ictal-appearing discharges (SIRPIDs): Nature and
clinical significance
Presenting author: Nicolas Gaspard
Collaborating authors: Nishi Rampal, Brandon Foreman, Ognen A. Petroff, David Greer, Tore Eid, Hitten
Zaveri, Irina Goncharova, Jan Claassen, Lawrence Hirsch
Continuous EEG recordings (CEEG) in the critically ill have revealed the common occurrence of highly
epileptogenic patterns induced by various alerting stimuli, termed SIRPIDs (stimulus-induced rhythmic,
periodic or ictal-appearing discharges). To date, their pathophysiological basis and clinical significance remain
largely unknown. By analogy to other physiological and pathological EEG phenomena, it has been proposed
that SIRPIDs could arise via the stimulation of brainstem- thalamo-cortical arousal circuits in the setting of
hyperexcitable cortex. Whether or not some or all SIRPIDs are harmful to patients and require treatment is
unknown and essentially unstudied to date. In this project, we will first aim to define the neuroanatomical basis
of SIRPIDs. Using structural and functional imaging studies (MRI, including DWI and DTI) we will look for
brain regions whose injury or activity correlates with the presence and location of SIRPIDs. We will then look
for focal alterations in brain perfusion or metabolism, using perfusion and metabolic imaging techniques (MRI,
SPECT and/or MR spectroscopy) and brain microdialysis, to determine if SIRPIDs affect brain metabolism.
Metabolic studies, either with MRS, brain microdialysis or using blood markers such as neuron-specific enolase
(NSE), will also help us clarify if SIRPIDs cause significant brain injury. Finally, we will conduct two short,
prospective trials: 1) comparing the short-term outcome of patients with SIRPIDs to a group of control patients
matched for age, primary etiology and level of consciousness; and 2) investigating metabolism, imaging and
NSE in a randomized, cross-over trial of patients with SIRPIDs, comparing standard care versus care with
minimal stimulation, in which nursing and other care will be synchronized and concentrated in short time
windows. Altogether, these data should help us clarify the nature and clinical significance of SIRPIDs and
determine if and when they require treatment.
Autism and epilepsy
Presenting author: Juan Torres-Reveron
Collaborating authors: Angélique Bordey
Autism spectrum disorders are diagnosed based on three features that include deficits in social communication,
absence or delay in language and stereotypy. About 30 % of autistic patients develop epilepsy and, although
controversial, this may lead to further delay in communication and loss of milestones. Around 50% of patients
with tuberous sclerosis complex mutations (TSC) are diagnosed with autism. Recent evidence suggests that the
cortical circuit as a whole may be in diasarray secondary to mutations in NLGN, SHANK3, TSC and activation
of the mTOR pathway. These mutations affect synapse formation and overall cellular metabolism.
Furthermore, a larger number of neurons are present at the layer 6/ white matter border in autistic patients, a
feature that is shared with some patients suffering epilepsy.
Our hypothesis is that autism, TSC and epilepsy share a common mechanism that is secondary to early
alterations in cortical excitability. We propose to use the TSC1+/- mouse model to examine these alterations.
These animals have impairment in social tasks similar to autistic patients. We will test whether a single
mutation of the TSC allele leads to decreased threshold for seizure generation using pentylenetetrazol.
Furthermore, we will examine the distribution of neurons at the layer 6/ white matter border to determine if the
model is similar to the human counterpart. Using electrophysiology, the spontaneous and evoked activity of
cingulate cortex’s layer 2/3 neurons will be compared to control animals to determine differences in synaptic
transmission.
Ambulatory seizure counting device
Presenting authors: Jason Gerrard, Robert Duckrow
A sizable fraction of patients with epilepsy are unaware of their seizures. This hinders clinical care and degrades
the outcome measure of most therapeutic trials, seizure frequency as recorded in a seizure diary. A seizure
counting device would allow the objective evaluation of treatment effects, establish intractability, and improve
patient safety. Recent advances in technology and seizure detection algorithms make the concept of an
ambulatory seizure monitor theoretically feasible. However, to be useful, a practical seizure detection and
counting device would have to be non-invasive and cosmetically appealing to be accepted by most patients.
This suggests development of a small scalp-based sensor that by necessity would have closely spaced
electrodes. It is not clear that such a small device placed over a restricted scalp region could detect epileptic
seizures. To address this question, recordings were obtained from patients during inpatient AV-EEG monitoring
using additional scalp electrodes placed adjacent (within 1.5 cm) to routine mastoid electrodes. The mastoid
area was chosen because it is behind the ear, relatively hair-less, and less likely to generate muscle artifact.
Preliminary review of recorded seizures demonstrates that characteristic electrographic patterns can be detected
using a single closely spaced bipolar derivation. Automated seizure detection using this signal and available
algorithms is ongoing. Demonstrating reasonable detection sensitivity and specificity would provide compelling
support for the development of a small non-invasive device that could be applied to the mastoid region of
epilepsy patients. Such a device would be simple to use, unobtrusive, and provide an objective record of seizure
timing and frequency.
Optogenetic testing of the network inhibition hypothesis in a mouse model of limbic
seizures
Presenting author: Jason Cromer
Collaborating authors: Joshua Motelow, Jessica Cardin, Hal Blumenfeld
Patients with temporal lobe epilepsy often experience loss of consciousness during focal limbic seizures despite
the fact that epileptic activity does not propagate throughout the cortex. Instead of cortical seizure activity, ictal
neocortical slow waves are observed in frontal and parietal cortex, which is similar to what is seen during sleep
or deep anesthesia. We have proposed that this neocortical slow activity is the result of a disruption of the
subcortical activating systems during these seizures. Thus, ictal inhibition of arousal nuclei causes loss of
consciousness due to the resulting decrease in excitatory neurotransmitters in the cortex (i.e., the network
inhibition hypothesis). Our lab has recently developed a rat model of limbic seizures, which like human
seizures, displays neocortical slow waves and reduced cerebral blood flow during partial seizures. Furthermore,
we have evidence of loss of activity in brain stem nuclei that are known arousal nuclei. However, these nuclei
are heterogeneous, and it has traditionally been impossible to manipulate specific cell types of a given nucleus
with standard electrophysiological techniques since electrical stimulation activates all subclasses of neurons and
passing axonal fibers near the stimulating electrode. In this talk, we will discuss our plans to develop a mouse
model of temporal lobe epilepsy in order to take advantage of recently developed optogenetic techniques.
Optogenetics allows the directed activation or deactivation of specific classes of neurons. Our goal is to utilize
optogenetics to better understand the basis for ictal neocortical slow activity by selectively manipulating
identified pathways related to arousal and consciousness during limbic seizures.